Rupert Murdoch's UK company could face a possible action for contempt of court over allegations that the News of the World penetrated Scotland Yard's highly secret witness protection programme.

Detectives working for the Operation Weeting inquiry into phone hacking are understood to have found evidence that the paper's £92,000-a-year specialist hacker, Glenn Mulcaire, targeted the voicemail messages of officers who were working on the programme.

Those officers have access to the new identities and current whereabouts of witnesses, victims of crime and offenders whose safety could be in jeopardy – information that is often the subject of a high court order prohibiting its disclosure.

A breach of such an order could be ruled to be a contempt of court, potentially leading to a fine or imprisonment. Any action would be brought by the attorney general's office, who are understood to be aware of the allegations.

Among those targeted by Mulcaire are Robert Thomson and Jon Venables, who as children murdered the Liverpool toddler James Bulger.

Mulcaire is due to be sentenced next week for conspiracy to intercept communications, alongside the tabloid's former editor Andy Coulson and three former news editors Neville Thurlbeck, Greg Miskiw and James Weatherup.

The Leveson inquiry heard that Operation Caryatid, the original police investigation into the News of the World, in 2006, found evidence in Mulcaire's computer suggesting that he may have penetrated the witness protection programme. Caryatid officers said they had no taken no action other than to pass a warning to the programme.

Murdoch's UK company, formerly known as News International and now News UK, already faces 12 criminal trials of its current or former journalists in London and in Scotland as well as continuing legal actions by victims not only of Glenn Mulcaire but also of the paper's second specialist hacker, Dan Evans, who has pleaded guilty to conspiracy to intercept communications and agreed to assist police.